1. Field of the Invention
The present invention relates to binders of magnetic recording media and, particularly, to compositions which show high dispersibility of finely-divided ferromagnetic powders and have excellent abrasion resistance.
2. Description of the Prior Art
Hitherto, cellulose derivatives, vinyl chloride-vinyl acetate copolymers, polyurethane resins, acrylic copolymers, vinylidene chloride polymers and copolymers, synthetic rubbers and polyesters, etc. have been used alone or as a mixture of them. Although nitrocellulose (nitro cotton) is able to disperse finely-divided ferromagnetic pigments quite well and imparts suitable tape characteristics when it is used as the binder for magnetic tapes, it has problems on handling thereof. Namely, it has defects that it has a property of spontaneous combustion and it is very easy to burn. Further, copolymers composed mainly of vinyl chloride, for example, vinyl chloride-vinyl acetate copolymers, are not satisfactory in the viewpoint of dispersibility of magnetic pigments. Further, combinations of other binders do not have sufficient properties in the viewpoint of high dispersibility to magnetic materials and abrasion resistance.